The present invention relates, in general, to methods of treating disorders of the eye, and, in particular, to methods of treating diseases characterized by elevated intraocular pressure (ocular hypertension), such as glaucoma. The invention further relates to compounds and compositions suitable for use in such methods.
Glaucoma is a disease of the eye that is characterized by an elevation in intraocular pressure. The elevation in pressure results from an impairment in the outflow of aqueous humor from the anterior chamber of the eye via the trabecular meshwork (see Tripathi et al, Drug Develop. Res. 27:191 (1992)). Treatments for glaucoma focus on decreasing intraocular pressure and thereby avoiding damage to the optic nerve. Left untreated, glaucoma can lead to blindness.
Numerous agents have been used for the treatment of glaucoma, however, many are accompanied by undesirable side effects, such as ocular pain and localized allergy. Examples of such agents include adrenergic amine, epinephrine, and cholinesterase inhibitors. Although topical application is typically used, absorption of at least certain of these compounds can result in adverse systemic effects including headaches, nausea and the like.
U.S. Pat. No. 4,757,089 discloses a treatment for glaucoma that involves the administration to the eye of ethacrynic acid or analogs thereof that react with sulfhydryl groups of the trabecular meshwork of the eye. Erickson-Lamy et al (Invest. Opthalmol. Vis. Sci. 33:2631 (1992)) have reported that ethacrynic acid, acting via a SH-reactive mechanism, induces cytoskeletal changes that result in the observed physiologic effects on outflow facility. WO 92/16199 discloses an improvement in the method described in U.S. Pat. No. 4,757,089 that involves the use of agents that mask the sulfhydryl reactive site as the drug passes into the eye. The masking agent dissociates in the eye thereby freeing the sulfhydryl reactive site for interaction with the trabecular meshwork. Use of such masking agents prevents side effects (such as corneal edema) that occur in the absence of the masks. (See also Epstein et al, Current Eye Res. 11:253 (1992).)
The present invention provides a further approach to glaucoma treatment. The present method involves the use of compounds that increase aqueous humor outflow but are non-SH reactive. The mechanism of action of the present compounds would thus appear to be distinct from that of ethacrynic acid and the analogs thereof disclosed in U.S. Pat. No. 4,757,089 and WO 92/16199.
It is a general object of the invention to provide a method of treating disorders of the eye.
It is a specific object of the invention to provide a method of treating glaucoma, or elevated eye pressure, by increasing aqueous humor outflow.
It is another object of the invention to provide a method of preventing the onset of glaucoma, for example, following cataract surgery.
It is a further object of the invention to provide compounds and compositions suitable for use in preventing or treating glaucoma, or elevated eye pressure, and to provide container means that include same.
In one embodiment, the present invention relates to a method of lowering intraocular pressure in an eye of a warm-blooded animal in need of such treatment. The method comprises administering to the eye a non-sulfhydryl reactive derivative of phenoxyacetic acid capable of increasing aqueous humor outflow in an amount sufficient to effect the treatment.
In another embodiment, the present invention relates to a method of preventing the onset of glaucoma in an eye of a warm-blooded animal in need of such prevention. The method comprises administering to the eye a non-sulfhydryl reactive derivative of phenoxyacetic acid capable of increasing aqueous humor outflow in an amount sufficient to effect the prevention.
In a further embodiment, the present invention relates to a pharmaceutical composition comprising a non-sulhydryl reactive derivative of phenoxyacetic acid and a pharmaceutically acceptable carrier, wherein said composition is in the form of an ointment, cream or gel.
In yet another embodiment, the present invention relates to a container having disposed therewithin a solution of a non-sulfhydryl reactive derivative of phenoxyacetic acid that increases aqueous humor outflow, wherein the container includes an outlet means suitable for dispensing the solution from the container in droplets.
Further objects and advantages of the present invention will be clear from the description that follows.
The present invention relates to methods of preventing and treating disorders of the eye characterized by elevated intraocular pressure, particularly, glaucoma. The present method results in an increase in aqueous humor outflow and thus a reduction in intraocular pressure that can be deleterious to the optic nerve.
Compounds suitable for use in the present method include non-SH-reactive phenoxyacetic acid derivatives, such as the anti-hypertensive agents indacrinone and ticrynafen, as well as non-SH-reactive derivatives thereof that increase aqueous humor outflow. The non-SH reactivity can be assessed, as described in the Examples below, by administering the compounds in combination with cysteine. Cysteine, which contains a reactive sulfhydryl group, has been shown in prior studies to be ineffective in influencing aqueous humor outflow. When administered in combination with ethacrynic acid, however, cysteine blocks the ability of that compound to increase outflow facility, thus indicating that ethacrynic acid exerts its effects by a sulfhydryl related mechanism (see U.S. Pat. No. 4,757,089). (See also Epstein et al, Current Eye Res. 11:253 (1992) and Tingey et al, Arch. Ophthal. 110:699 (1992)). Cysteine used in combination with non-sulfhydryl reactive phenoxyacetic acid derivatives does not block the ability of these compounds to increase outflow facility (see Examples).
Compounds suitable for use in the invention have a margin of safety of at least 2.0 and, advantageously, at least 4.0. That margin is measured as the ratio of the dosage of an aqueous humor outflow increasing compound that produces unacceptable side effects and the dosage that produces a clinically significant increase in aqueous humor outflow in a patient suffering advanced open angle glaucoma. Compounds suitable for use in the present method do not produce permanent or long term deleterious alterations in the eye.
The compounds of the invention can be formulated into compositions suitable for topical administration. Such compositions typically take the form of aqueous solutions that are administered dropwise to the eye. Alternatively, the compounds can be formulated into gels, ointments or creams that can be applied topically to the tissue surrounding the eye. The compounds of the invention can also be formulated into sterile solutions for administration by intracameral injection into the anterior chamber of the eye, for example, at the time of cataract surgery in order to avoid the postoperative onset of glaucoma. Administration by direct injection into the trabecular meshwork of the eye can also be effective (by way of example, see Melamed et al, Am. J. Ophthal. 113:508 (1992)). The compounds of the invention can also be administered to the eye by iontophoresis (see, for example, Grossman and Lee, Ophthalmology 96:724 (1989); Sarraf et al, Amer. J. Ophthal. 115:748 (1993); Sarraf et al, Invest. Ophthalmol. Vis. Sci. 34 (ARVO Suppl):1491 (1993)). Systemic administration of the compounds of the invention is also contemplated, either oral administration or intravenous administration. In the case of oral administration, a suitable composition is in dosage unit form and is a pill, capsule, tablet or the like. Compositions suitable for intravenous administration are typically formulated as sterile solutions.
Whatever the mode of administration, the compositions of the invention include, as active agent, the non-SH-reactive phenoxyacetic acid derivative, and a pharmaceutically acceptable carrier. The compositions of the invention can also include agents that promote or enhance delivery, such as surfactants and wetting agents, benzalkonium being one such agent. The compositions can also include preservatives that prolong shelf life.
The amount of active agent to be included in the composition will vary with the phenoxyacetic acid derivative, with the dosage regimen used and with the effect sought. Preferred concentrations can be readily determined. Likewise, the optimum amount of phenoxyacetic acid derivative to be administered to any particular patient can be determined without undue experimentation.
The compounds and compositions of the invention can be provided in various container means. Compositions to be administered topically can be provided as sterile solutions in a container means that facilitates administration of the solution to the eye in drops. For example, the container means can include an outlet that allows for the dispensing of drops directly or, alternatively, the container means can include a separate dropper means reversibly associated therewith. Compositions to be administered topically that are formulated as creams, gels or ointments can be provided in container means that facilitate administration to the eye or surrounding tissue. Compositions to be administered by injection, intravenously or into the eye or surrounding tissue, can be provided as solutions in sterile container means.
The compounds and compositions of the invention are suitable for use in any mammal suffering glaucoma. While human treatment is the focus of the invention, veterinary use is also contemplated.